The Zika virus is spread by the Aedes Aegypti mosquito (photo by Marcos Freitas via flickr)

Two days following an announcement by the World Health Organization (WHO) that Ebola is no longer an international public health emergency, two U of T public health leaders spoke to alumni about the latest global infectious disease epidemic, the Zika virus.

Among the subjects discussed by Dr. Ross Upshur andDr. Vanessa Allen were Zika's link to microcephaly and whether the 2016 Summer Olympics should be cancelled.

“It’s not a coincidence that Ebola and Zika outbreaks happened in poor countries and poorer areas of developing counties," said Upshur, a professor of clinical public health at the Dalla Lana School of Public Health. "This underlines the desperate need for global investment in health equity.”

Close to 100 alumni, students and faculty attended In the Loop – the first of a new event series hosted by the Public Health Alumni Association where alumni, students and friends will learn about cutting-edge public health issues – on March 30 at the Dalla Lana School of Public Health.

“The biggest lesson learned from Ebola is that we need to create health systems on the basis of strong primary care with close links to public health,” Upshur continued, noting that WHO officials declared Zika a public health emergency much sooner than they did in the context of Ebola, which accelerated the response.

“Brazilian health authorities are handling this outbreak reasonably well by linking surveillance with public health action, which generates good data on which authorities can make informed policy decisions,” he said. "And we’re seeing better forward planning from neighbouring countries like Colombia, which is very promising.”

Allen, who is Public Heath Ontario’s chief microbiologist, explained that although many believed Zika arrived in South America during the 2014 World Cup in Brazil, a study published on March 24 in Science suggests the virus likely arrived in Brazil through increased travel patterns from the South Pacific region between May and December 2013, more than a year before the outbreak was detected.

The study – the first genomic analysis of Zika – was conducted by a large international team of researchers, including Dalla Lana associate professor Kamran Khan and assistant professor Marisa Creatore. Read more about the study in the Toronto Star.

Between 2013 and 2015, there have been more than 190,000 suspected and confirmed cases globally, with the vast majority occurring in rural areas of Brazil. Scientists believe that up to 80 per cent of people infected with Zika never experience symptoms, which means its link to microcephaly – a birth defect associated with underdeveloped brains – is particularly challenging to understand.

“Microcephaly has many potential causes and its connection to the Zika virus is an association,” said Allen, an assistant professor in U of T’s department of laboratory medicine and pathobiology. “It’s not a proven fact that mothers infected with the virus will have babies with microcephaly.”

Before Zika, there were 100-150 microcephaly cases each year in Brazil. In 2015, there were more than 5,000 cases, Allen said.

Allen also touched on the sexual transmission of the virus. Scientists have found that the virus can be transmitted through sexual contact and it remains active in semen up to 62 days after symptom onset. She noted a handful of cases where females whose husbands had travelled to South America tested positive for the virus even thought they had not travelled anywhere affected.

This emerging sexual transmission link has important considerations for those of reproductive age attending the 2016 Summer Olympics in Rio de Janeiro.

“I don’t think the Olympics should be cancelled, but all athletes and visitors should consult public health organization websites for the latest information on how to reduce risks,” said Upshur, noting that it’s a dynamic situation and organizations such as the Public Health Agency of Canada and the Center for Disease Control and Prevention will have the most up-to-date information.

Regardless of the imminent influx of global Olympic travellers, health professionals and policy-makers consistently face challenges when making evidence-based decisions during epidemics because of the emerging nature of research. One student asked the speakers how public health professionals can overcome this challenge.

“During an infectious disease outbreak, strong relationships between government and public health agencies, like Public Health Ontario and the Ministry of Health, is particularly crucial,” said Upshur. Ontario has done a good job at creating systems with a two-way flow of knowledge and policy.”